Printing technologies generally provide alternative methods to relatively laborious, wasteful, and expensive lithographic techniques for the fabrication of electronic devices and/or integrated circuits. However, advanced techniques and materials that allow for the fabrication of integrated circuits on a variety of substrates using selective deposition, printing and/or imaging technologies are still desired. In printing processes, materials in the form of liquid inks may be selectively deposited (e.g., printed) using techniques such as inkjet printing, gravure printing, screen printing, etc. Because printed electronics is an emerging technology, a limited number of inks are commercially available, and such inks provide a limited number of materials for fabricating electronic devices. Therefore, there is a continued need to develop new inks that not only can be printed using different techniques, but that also expand the palette of materials for fabricating printed devices and provide a variety of different process integration schemes.
In integrated circuits, the devices (e.g., TFT, capacitors, diodes, etc.) are generally connected to each other with metal lines (i.e., interconnects). Integrated circuits with good performance generally include interconnects with low resistivity, and thus not all metals are suitable for use as interconnects. Typical examples of suitable metals are Al, Cu, Au and Ag. Often, metals used for interconnects in integrated circuits do not form low resistivity contacts with the device electrodes (e.g., gate and source/drain electrodes), which are usually made with n+ and/or p+ doped silicon. Therefore, in order to fabricate integrated circuits with good performance, a contact layer formed between the n+/p+ silicon and the metal lines often provides relatively low resistivity between the devices and the interconnects. Typically, silicides are the preferred contact layers used in microelectronic devices, because they can provide ohmic contacts to heavily doped semiconductors (e.g. n+/p+ silicon and/or germanium).
In a process for making printed electronic devices, it is desirable to minimize the number of inks and the number of printing steps to fabricate printed integrated circuits. Therefore, there is a need to develop a metal ink that has high conductivity and that forms low resistivity contacts with n+/p+ silicon, thus eliminating the need for separate inks for the metal interconnect and for contacts between doped silicon and the metal interconnect.